Typically, in a cellular radio telecommunications system such as GSM or UMTS, the whole system coverage area is divided into smaller sub-areas, termed “logical cells”. In general, the logical cells are defined by the transmission of the downlink common channels: in the neighbouring logical cells the downlink common channels are typically transmitted on different frequencies and/or using different scrambling codes or with other types of identifiers.
Within each logical cell the amount of radio resources is usually limited. That is why, in order to serve a higher user density, the size of the logical cells has to be made smaller. Furthermore, since the system resources are also limited, for example the number of frequencies and the number of scrambling codes, the same frequencies or scrambling codes must be re-used (although only for cells which are spaced apart sufficiently to avoid cross-cell interference).
U.S. Pat. No. 5,889,494 teaches a system and method for dynamically sizing sectors of a multi-sectored radiation pattern used in a cellular telecommunication system.